The present invention relates to a speed-changing gear manufacturing apparatus, more specifically a speed-changing gear manufacturing apparatus for forming back tapered spline teeth on a gear material.
Conventionally, on a speed-changing gear used for manual transmission, etc. are formed spline teeth having a chamfer at the tip and having both side faces formed in the shape of back taper (hereinafter referred to as xe2x80x9cback-tapered spline teethxe2x80x9d in some cases), and speed change teeth composed of spur gear or helical gear.
As apparatus for manufacturing this back-tapered spline teeth of speed-changing gear by forging only without cutting work, there is one which is disclosed in the Japanese Provisional Patent Publication No. 63-120958, for example.
This speed-changing gear manufacturing apparatus is constructed in a way to form both side faces of spline teeth in back-tapered shape by pressing, by means of a pressing member, a plural number of dies disposed at regular intervals on a circumference, so that they may move on the lines extending radially from the center axis of the gear material, between spline teeth having parallel side faces formed in advance on the gear material, and moving them toward the center axis of the gear material.
By the way, said conventional speed-changing gear manufacturing apparatus had an advantage of being capable of forming both side faces of spline teeth in back-tapered shape with high accuracy, by means of a plural number of dies disposed at regular intervals on a circumference.
However, a problem with this speed-changing gear manufacturing apparatus was that, when forming both side faces of the spline teeth in back-tapered shape, dispersion is produced in the shape of the chamfer or in the height of back-tapered spline teeth, because the chamfer formed in advance on the tip of the spline teeth is not restricted by the die or other member.
In view of the problems inherent with said conventional speed-changing gear manufacturing apparatus, the objective of the present invention is to provide a speed-changing gear manufacturing apparatus capable of forming back-tapered spline teeth having a chamfer at the tip with high accuracy, by forming both side faces of spline teeth in a back-tapered shape and forming the tip in a chamfered shape at the same time.
To achieve said objective, the speed-changing gear manufacturing apparatus according to the present invention is a speed-changing gear manufacturing apparatus comprising dies formed at regular intervals on a circumference, to enable it to move a plural number of spline teeth forming units for forming back-tapered spline teeth on the lines extending radially from the center axis of the gear material, and a pressing member for moving the spline teeth forming units toward the center axis of the gear material, by pressing the outer circumferential face of the spline teeth forming units of the dies, characterized in that said spline teeth forming units are constructed in a way to form an open space in which to form both side faces of spline teeth in a back-tapered shape and form the tip in a chamfered shape at the same time, in contact with the adjacent spline teeth forming units and between two adjacent spline teeth forming units, by moving the spline teeth forming units toward the center axis of the gear material.
This speed-changing gear manufacturing apparatus, constructed in a way to form an open space in which to form both side faces of spline teeth in a back-tapered shape and form the tip in a chamfered shape at the same time, in contact with the adjacent spline teeth forming units and between two adjacent spline teeth forming units, by moving the spline teeth forming units of the dies toward the center axis of the gear material, is capable of forming both side faces of spline teeth in a back-tapered shape and forming the tip in a chamfered shape at the same time, and capable of forming back-tapered spline teeth having a chamfer at the tip with high accuracy.
And, the speed-changing gear manufactured in this way, which is uniform in chamfer shape and height of the back-tapered spline teeth, enables a smooth speed-changing motion using a manual transmission, etc. when required.
In this case, said dies may be constructed in such a way to have an arced shell in which are formed slits at regular intervals in a longitudinal direction up nearly to the bottom part, form spline teeth forming units at the top end of the respective shells split by said slits, and support the bottom face of the spline teeth forming units of the dies with die holders formed on the sloped face rising toward the center axis of the gear material.
This will enable the spline teeth forming units of the dies to automatically return, after forming back-tapered spline teeth having a chamfer at the tip, with a restorative force of the shell formed in an arced shape.
Moreover, this enables the simplification of the manufacturing apparatus structure, facilitates maintenance work, and reduces the manufacturing and maintenance costs of the manufacturing apparatus.
Furthermore, this makes it possible, when moving the spline teeth forming units toward the center axis of the gear material, by pressing the outer circumferential face of the spline teeth forming units of the dies by means of a pressing member, to prevent the spline teeth forming units from turning around the bottom part of the dies, thus enabling it to form back-tapered spline teeth having a chamfer at the tip with higher accuracy.
Additionally, it becomes possible to reduce the radial direction force applied to the shells formed with the arced shape of the dies through the spline teeth forming units.
In this case, said dies may be constructed in such a way to be split into the same number as the number of spline teeth to be formed, and to form spline teeth forming units at the top end, the split dies being disposed in an annular shape, and fastened at the bottom end by means of a fastening fixture.
This makes it possible to easily manufacture dies provided with spline teeth forming units.
Yet more, this enables, even in cases with any wear or damage to the spline teeth forming units, to replace the dies only in the part concerned, thus facilitating maintenance and reducing the cost of the manufacturing apparatus.
In addition, said dies may be constructed with die elements, split in the same number as the number of spline teeth to be formed and forming spline teeth forming units at the top end, and die element holders disposed and held in an annular shape to enable the die elements to move on a line extending radially from the center axis of the gear material.
This makes it possible to easily manufacture dies provided with spline teeth forming units.
Moreover, this enables, even in cases with any wear or damage to the spline teeth forming units, the replacement of dies only in the part concerned, thus facilitating maintenance and reducing the cost of the manufacturing apparatus.
And, it is possible to form a sliding piece on the inner circumferential side of each die element, and slidably support it with a die element pressing device fixed to the material receiving base.
This makes it possible to slide the split die elements with good accuracy, and form highly accurate spline teeth.
Furthermore, it is possible to dispose, at the center of the die element holder, a die element returning ring forming a sloped face at the outer circumferential edge, to make the respective die elements return in an upward motion after the forming of the spline teeth.
This enables the accurate removal of gear material after forming from among the dies with a simple device.